ruby-noise isn't quite packaged as a gem or anything - its just a few method definitions for composing wave generators and playing them with PortAudio.

In addition to the source repository, episode co-host David Bock published this gist last night that shows how to use it to compose complex audio waveforms with FM Synthesis, as well as demonstrate the mathematical relationship between notes in Western music.

Another entry in the 'lets add the database schema to the model as comments' series of gems, this one has a neat feature - you can add comments describing the purpose of a field, and they will be preserved if you need to re-run the rake task that creates the annotation.

This is a 'glue' gem that integrates the Money gem with your ActiveRecord models. You can have dollar amounts associated with your models, and have them stored as different currencies. If you provide exchange rates, it'll even convert the values for you.